//给你单链表的头节点 <code>head</code> ，请你反转链表，并返回反转后的链表。
//<div class="original__bRMd">
//<div>
//<p> </p>
//
//<p><strong>示例 1：</strong></p>
//<img alt="" src="https://assets.leetcode.com/uploads/2021/02/19/rev1ex1.jpg" style="width: 542px; height: 222px;" />
//<pre>
//<strong>输入：</strong>head = [1,2,3,4,5]
//<strong>输出：</strong>[5,4,3,2,1]
//</pre>
//
//<p><strong>示例 2：</strong></p>
//<img alt="" src="https://assets.leetcode.com/uploads/2021/02/19/rev1ex2.jpg" style="width: 182px; height: 222px;" />
//<pre>
//<strong>输入：</strong>head = [1,2]
//<strong>输出：</strong>[2,1]
//</pre>
//
//<p><strong>示例 3：</strong></p>
//
//<pre>
//<strong>输入：</strong>head = []
//<strong>输出：</strong>[]
//</pre>
//
//<p> </p>
//
//<p><strong>提示：</strong></p>
//
//<ul>
//	<li>链表中节点的数目范围是 <code>[0, 5000]</code></li>
//	<li><code>-5000 <= Node.val <= 5000</code></li>
//</ul>
//
//<p> </p>
//
//<p><strong>进阶：</strong>链表可以选用迭代或递归方式完成反转。你能否用两种方法解决这道题？</p>
//</div>
//</div>
//<div><div>Related Topics</div><div><li>递归</li><li>链表</li></div></div><br><div><li>👍 2230</li><li>👎 0</li></div>

//leetcode submit region begin(Prohibit modification and deletion)
/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode reverseList(ListNode head) {
        if(head == null || head.next==null ){
            return head;
        }
        ListNode cur = head;
        ListNode prev = null;
        while(cur!=null){
            ListNode temp= cur.next;
            cur.next = prev;
            prev = cur;
            cur = temp;
        }
        return prev;
    }
}
//leetcode submit region end(Prohibit modification and deletion)
